Radio-labelled proteins have numerous medical, biological, clinical, scientific and other applications. Interferons, specifically, labelled with .sup.125 I have been used for binding and crosslinking studies (1, 17, 27-32, 34-37)..sup.1 Human IFN-.alpha.'s, -.beta., and -gamma have all been radio-iodinated by various procedures (reviewed in Pestka et al (2)). However, proteins labelled with radioactive iodine have serious well-known disadvantages and hazards.
 FNT .sup.1 The scientific publications, patents or other literature ("publications") to which reference is made herein are referenced by numerals and identified further towards the end of this text. All of these publications are incorporated herein by reference.
The study of cell surface receptors for the interferons requires radio-labelled interferons, such as interferons labelled with .sup.125 I with high biological and high radio-specific activity. Several years ago, it was found that interferon gamma.sup.2 can be phosphorylated to very high radio-specific activity while retaining biological activity (3, 4). Thus, [.sup.32 P]Hu- and Mu-IFN-gamma were used for studying the human and murine IFN-gamma receptors, respectively (5, 6, 9). These studies were carried out by phosphorylating human and murine interferon gamma (Hu- and Mu-IFN-gamma) with cyclic AMP-dependent protein kinase from bovine heart muscle and [gamma-.sup.32 P]ATP (3). These phosphorylated and .sup.32 P-labelled interferons have provided valuable reagents (3, 4) of high radio-specificity to study cell surface receptors (5, 6) and to identify the chromosome encoding the gene for Hu-IFN-gamma (7, 8) and Mu-IFN-gamma (9) receptors. For all of these studies and applications, interferons which are phosphorylated are most useful. Several reports identified the phosphorylation sites of Hu- and Mu-IFN-gamma as serine residues near the COOH termini (4, 5, 10, 11).
 FNT .sup.2 The abbreviations used have followed standard nomenclature as described in detail in Methods of Enzymology, Interferons, Vol. 119, Part C, Edited by Sidney Pestka, Section I, Introduction (Reference 25). In brief, interferon alpha, beta, and gamma are designated IFN-.alpha., IFN-.beta., and -gamma, respectively. The species of origin is designated by a prefix Hu, Mu, Bo, etc. for human, murine, or bovine species, respectively, as Hu-IFN-.alpha., Hu-IFN-.beta., or Hu-IFN-gamma, for example.
However, under conditions used for the phosphorylation of IFN-gamma, it was reported that Hu-IFN-.alpha.A and Hu-IFN-.beta. cannot be phosphorylated by the cyclic AMP (cAMP)-dependent protein kinase (2, 3). A review of the phosphorylation of the various classes or groups of interferons and other proteins (1, 3, 4, 20, 21, 22, 38, 39, 40, 64) confirms that researchers have not successfully phosphorylated Hu-IFN-.alpha. or Hu-IFN-.beta. under conditions under which gamma interferons have been phosphorylated. It has been reported indeed that recombinant IFN-.alpha. and IFN-.beta. were not phosphorylated (3) and as a consequence it was uncertain whether an available site was present.
In the light of problems with iodinated compounds and limitations for use of iodinated IFN-gamma, it is understandable that there is a keen interest and need in making available phosphorylated Hu-IFN-.alpha. and -.beta. which can be labelled for numerous practical, scientific and commercial applications.
Likewise, there is such interest and need for other phosphorylated--and labelled--polypeptides which are not available yet in such chemical configurations. For example, a phosphorylatable tumor necrosis factor (TNF) would be valuable to study the receptor for TNF. TNF is not phosphorylatable with the cAMP-dependent bovine heart kinase. Indeed, it has been reported that interest in protein phosphorylation has increased enormously over the past few years (38, 39).
The invention as will be described in detail hereinafter contributes to meeting these and other needs.
By way of further background to the invention, the term "interferon" describes a family of animal proteins which possess antiviral, antiproliferative and other potentially useful properties. There appear to be three major classes of interferons: leukocyte (or alpha interferon), fibroblast (or beta interferon) and immune (or gamma interferon) (1, 2). Detailed description of interferons is found in various publications including in references 1, 2, U.S. Pat. Nos. 4,727,138; 4,734,491; 4,737,462, and many others; various hybrid human leukocyte interferons are described in U.S. Pat. No. 4,414,150 and in reference 46. In general the standard class of human IFN-.alpha.'s are polypeptides of 165-166 amino acids (see reference 1 for details of human and non-human interferon-.alpha. species); some species have been isolated that lack the 10 COOH-terminal amino acid residues; and some species of IFN-.alpha. are glycosylated. The amino acid sequences of Hu-IFN-.alpha. species and of Hu-IFN-.beta. derived from cDNA or genomic DNA sequences are described in (1, Section I). Recombinant DNA-derived interferons including Hu-IFN-.alpha., -.beta., and -gamma and corresponding interferons from other animal species are likewise well described (1, 2). Various modifications of human and murine interferons have been reported. New non-natural human and murine interferons with often markedly changed biological properties have been constructed (1, 24, 45). The terminology "non-natural" is a term of art which refers to recombinant DNA interferons obtained by altering the nucleotide sequence of coding cDNAs (45).
The term "Hu-IFN-.alpha." as used herein is intended to include all different species of alpha interferons. A large number of DNA sequences corresponding to the interferons from various species have been isolated and identified. Likewise various IFN-.beta.s and IFN-gamma(s) are disclosed. The invention encompasses all of these members of the family (reference 1, pages 5-14).
The term "native" as used herein refers to the proteins, e.g., interferons, which proteins are naturally produced; "synthetic" and "non-natural" refers to proteins produced by synthetic or DNA-recombinant procedures, either type which do not contain a phosphorylatable site (or where the phosphorylatable site is inaccessible, for instance due to the configuration of the protein), which protein in accordance with the invention is to be phosphorylated.
This invention contemplates and includes all interferons native, natural, modified, or recombinant DNA interferon-like proteins which are modifiable by introduction of one or more phosphate or analog groups. All of these interferons and others known in the art or to be known are within the contemplation of the invention. The present invention is principally concerned with various modified proteins or polypeptides, and alpha and beta interferons.
When reference is made to IFN-alpha, the term is intended to cover and include the various alpha species.
The term "modified" is used in this invention broadly, and means for instance, when reference is made to proteins, a protein which has been provided with a phosphorylatable site or provided with a phosphorus label (or analog label). The nucleotide sequences which code for such amino acid sequences which contain a putative phosphorylation site are also designated as "modified", when appropriate.
The term "unphosphorylatable" protein means a protein which normally has not been phosphorylatable (or phosphorylated) for whatever reason, e.g., either because it does not contain a putative phosphorylatable site and correspondingly, the DNA sequence which codes for the protein does not contain the DNA sequence coding for the putative amino acid recognition sequence; or because such site is not accessible for phosphorylation.
The term "provided with" or "having provision(s) for" or like terminology is used in this invention broadly, and means both "fused" and "inserted". Illustrative are the hybrid-fused Hu-IFN-.alpha.A/gamma (illustrated in FIG. 1) and Hu-IFN-.alpha.A-P1, -P2 and -P3 (illustrated in FIG. 8), respectively. Thus, the nucleotide insert can be within the coding region of the gene at one end thereof or anywhere within the coding region. These variants are all considered to be within the term "modified," which can refer to the amino acid sequence or to the nucleotide sequences, as will become apparent from the description hereinafter.
The term "comprises" or "comprising" covers and includes all situations regardless where the amino acid recognition sequence (or the nucleotide sequence coding for it) is located.
By way of further background in the preferred method of the invention, phosphorylation is carried out by means of a protein kinase. Protein kinases catalyze the transfer of the gamma phosphoryl group of ATP to an acceptor protein substrate. However, as described herein the invention is not limited to kinases for which the acceptor site is a particular amino acid (like serine) but includes also those for which the site is another amino acid in the sequence, and in general includes protein kinases as a whole.
The term "protein" (or polypeptide) as used herein is intended to include glycoproteins (as well as proteins having other additions). A case in point is that of natural Hu-IFN-.beta. which has been shown to be a glycoprotein; when produced in E. coli by recombinant DNA techniques, Hu-IFN-.beta. is not glycosylated. Glycosylated interferons have been reported to be obtained by expressing the proteins in animal cells or in yeast (as is discussed in reference 1 at pps. 383-433 and 453-464; and in references 48-55, 84-92).
The term "biological activities" or like terms as used herein in conjunction with proteins is intended to be interpreted broadly. In the case of the interferon-like proteins, it includes all known (or to be discovered) properties including properties specific to Hu-IFN-.alpha.'s or to Hu-IFN-.beta. or common to both, such as their antiviral activity and their capability to modulate antigens of the major histocompatibility complex (MHC), in particular to induce an increase in surface expression of class I MHC antigens, including .beta..sub.2 -macroglobulin.
"Functional" proteins are proteins which have a biological or other activity or use.
The term "active areas" or "biologically active" areas or segments or equivalent terminology often refers to the presence of a particular conformation or folding of the protein molecule, or for instance, to specific disulfide bridges between specific amino acids in the sequence, but of course is not limited thereto.
The term "vector" as used herein means a plasmid, a phage DNA, or other DNA sequence that (1) is able to replicate in a host cell, (2) is able to transform a host cell, and (3) contains a marker suitable for identifying transformed cells.
Throughout the description of the invention and the claims, and following convention, the "singular" includes the "plural"; for instance, a phosphorylatable or phosphorylation site, means at least one such site, unless indicated otherwise.
Other terminology used herein will become apparent from the description which follows.